2 Replies

That is just a protocol to define any method. It has been in existent since C and we have been following it in the subsequent programming languages. And Update is also a method which Unity call in for every Time.deltaTime.

As you can see in the example, brackets are used to define the body of the method. You can also insert arguements into the parenthesis of a methed, like this:

// This takes a number as an argument and adds 1 to it
void foo(aNumber){
aNumber += 1;
}

I highly suggest you familiarize yourself with basic programming techniques before doing anything in Unity. Otherwise you'll keep coming back here and flooding UnityAnswers with incredibly basic questions like this. Sorry but I have to downvote the question, it doesn't belong here. Google "basic programming" and do some tutorials.